Various tools have been known in the past for working with cements, concretes, mastics and/or muds to, for example, prepare, apply and finish a desired shape or smooth surface for various building surfaces. For example, some tools used for preparing the surface of, for example, concrete, include trowels. Another example are various tools used to prepare and finish, for example, mastics and mud for drywall, including, flat boxes, corner finishing boxes, joint boxes, and automatic taper (taping) machines. Some examples of various previously known flat boxes may be found in U.S. Pat. Nos. 2,824,442; 2,984,857; 3,888,611; 4,516,868; and 7,318,716, among others. In any case, regardless of type, these tools are typically hand tools that are used to apply and/or smooth various building surfaces such as floors and walls and result in skilled craftsman working on a number of surfaces for long periods of time during the work day.
One particular example of the flat box or finisher applicator 100 is illustrated in FIG. 1A and is typically made in the form of a container or housing that has a plurality of side walls, e.g., side wall 105 and front wall 110. The top of the container or housing is typically provided by a movable pressure plate 115 which is used to drive out the mud through an output port (usually in a bottom wall opposite the pressure plate that is not shown in this figure) when force is applied to the movable pressure plate 115 by the user. A set of wheels, e.g., wheel 121, may typically be attached to at least one side of the container or housing on either ends so as to enable more easy motion of the container or housing along the wall or working surface while in use when forming a relatively flat smooth layer of mastic or mud upon the wall or working surface. The moveable pressure plate 115 may be urged outward by a one or more spring(s) 116 and held closed by one or more movable tab(s) 117 attached to the container or housing with a screw 118. The various sides (e.g., 105, 110, etc.) of the container or housing may be held together using rods that run lengthwise along inside or outside the housing or container, and nuts, e.g. nuts 135 and 135, on either ends of the rods (only one end shown). Further, the flat box or finisher applicator 100 includes a blade (not shown) and a blade holder 125 that holds the blade and smoothes and distributes mastic or mud that is pushed out of the container or housing by the pressure plate 115. The blade holder may be made of a rigid metal bar and have a plurality of evenly spaced vertical cuts or slits 130 cut into it so as to improve flex. The blade holder is made to flex by a blade adjustment system including a flat spring 120 and a tension adjustment knob 122. The tension adjustment knob 122 is attached a bracket 119 that is attached to the front wall 110 of the container or housing 110. The blade holder 125 is held to the container or housing by a plurality of plates 132 attached to the side wall(s) 105 by screws 133 that penetrate the wall 133.
Referring now to FIG. 1B, an exemplary prior art mastic or mud shaping and distribution system is provided. In this case a blade 115 is a slightly bowed flat elongated piece of metal that may be place into a channel cut lengthwise in a blade holder 125. The blade holder 125 is made of a uniform cross of brass material that is periodically partially cut along its length (e.g., vertical cut or slit 130) and these cuts are uniformly distributed in order to get the needed flex from the inherently stiff brass material. The resulting mud flow pattern is generated by the user adjusting the tension of a flat spring based system, spring 120, knob 122, and pins 157A and 157B (held to the spring 120 by screws 160A and 160B), that applies forces that resist the flexing of the blade which occurs as the mud flows under the blade 115 and blade holder 125 assembly. In some prior art systems, the blade holder is produced from a uniform cross section of plastic material. In this case, the plastic blade holders typically have uniform cross section with no periodic cutting due too the reduced stiffness of the plastic material. The blade and blade adjustment system are held in place and attached to the front wall by a bracket 155 and 170. In this example, the mud flow pattern is generated by moving the center region of the blade assembly to a positive position (downward) by turning the knob 122 to a desired position. The resulting mud pattern on the wall is then a result of the gap created by the blade flexed shape with the blade center region displaced and the blade end regions held in contact with the wall.
In all previously known designs, the mud flow pattern is generated by the flexed shape of a blade and blade holder assembly which has a stiffness which is uniform along its length. Those skilled in the art will know that a uniform geometry along the length of a flexing blade will result in a relatively common shape to the mud flow pattern because the stiffness of the blade assembly will result in a flexed geometry that is consistent regardless of the material used for the blade holder.
These types of tools, for working with cements, concretes, mastics and/or muds, are typically exposed to bumps and mechanical stresses, as well as corrosive substances in their use. Therefore, it is advantageous to build such tools to be cost effective, light in weight and durable against extensive use and stress, as well as the corrosion from corrosive materials they are designed to work on (e.g., concrete, mastic, mud, etc.). Further, it is advantageous for these tools to apply a quality surface coating which requires a minimum amount of subsequent process to yield a desired finished surface contour or shape.